Calvera: A low-mass strangeon star torqued by debris disk?

Calvera is a \(59\,\mathrm{ms}\) isolated pulsar, being unique due to its non-detection in radio, optical and gamma-rays but the purely thermal emission in soft X-rays. It is suggested that Calvera could be an ordinary middle-aged pulsar with significant magnetospheric activity at a large distance....

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Bibliographic Details
Published in:arXiv.org 2017-09
Main Authors: Li, Yunyang, Wang, Weiyang, Ge, Mingyu, Liu, Xiongwei, Tong, Hao, Xu, Renxin
Format: Article
Language:English
Subjects:
Accretion disks
High temperature
Neutron stars
Neutrons
Observatories
Pulsar magnetospheres
Pulsars
Soft x rays
Stellar magnetic fields
Thermal emission
X-rays
XMM (spacecraft)
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Summary:Calvera is a \(59\,\mathrm{ms}\) isolated pulsar, being unique due to its non-detection in radio, optical and gamma-rays but the purely thermal emission in soft X-rays. It is suggested that Calvera could be an ordinary middle-aged pulsar with significant magnetospheric activity at a large distance. Alternatively, it is proposed in this paper that Calvera is a low-mass strangeon star with inactive magnetosphere (dead). In this scenario, we jointly fit the spectra obtained by the {\it XMM-Newton} Observatory and the {\it Chandra} X-ray Observatory with the strangeon star atmosphere model. The spectral model is successful in explaining the radiation properties of Calvera and X-ray Dim Isolated Neutron Stars, both showing similar observation features. Within the dead pulsar picture, Calvera might be of high temperature at \(0.67\,\mathrm{keV}\), possessing a small stellar radius \(R\la4\,\mathrm{km}\) and a presumably small magnetic field \(B\la10^{11}\,\mathrm{G}\) and is probably braked by the fall-back disk accretion. Future advanced facilities may provide unique opportunities to know the real nature of Calvera.
ISSN:2331-8422
DOI:10.48550/arxiv.1709.07679